I wasn't confused about the railing vs. stairs, that was quite clear in the original post. But it sounds like you signed a contract with an open ended price after getting a second contractor bid for $4800 and now the first one is saying $11-$14K. Wow. I like what GN Builders said, get more estimates. I recently got 4 bids for mudjacking a sinking driveway, and they varied from $978 to $4600. Not taking either the high or the low - it's going to be about $2k. Incredible what stuff costs. But unless you do it yourself or have a woodworker friend, you're at the mercy of the market. If you have kids, get them interested in mechanical trades, either as a hobby or career. You'll help increase the labor pool and competition, and they can do stuff for you free. :-D

Be sure to sell or give away that beautiful old railing and not throw it on a heap. I happen to like it. But indeed, it might look better in black. The railing you have posted instead gave me some shudders. Quite a contrary style and not one I'd welcome in my home. Way too modern for a ranch home, is what comes to my mind. If you are really going to get a new railing, I like the one Judy proposed, although I wouldn't want it in white at your place. Perhaps in black and the railing that matches the wood of the stairs? Or maybe something like this?

It will cost you just as much to paint as to sand and stain. Another vote to please not paint, especially not grey or black. The floor and front door color is lovely, I hope you are not changing. I would keep the beams the same. The dark floors and beams contrast nicely with the walls. What do you mean by as we are painting trim outside that black or grey? Most of the grey exteriors I see look like small prisons.

Know your area's building codes before you start. What you like and what is to code for your area may not line up. A licensed contractor should know if you can't find any information on your city's website.